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Spatial distribution of human cell survival and oxygen effect in a therapeutic helium ion beam
Author(s) -
Todd Paul,
Martins Bambino I.,
Lyman John T.,
Kim J.H.,
Schroy Carter B.
Publication year - 1974
Publication title -
cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.052
H-Index - 304
eISSN - 1097-0142
pISSN - 0008-543X
DOI - 10.1002/1097-0142(197407)34:1<1::aid-cncr2820340102>3.0.co;2-h
Subject(s) - bragg peak , beam (structure) , irradiation , helium , oxygen , ion beam , nuclear medicine , atomic physics , optics , materials science , medicine , physics , nuclear physics , quantum mechanics
The survival of human kidney T‐1 cells, based on colony formation, was determined in the presence and absence of oxygen as a continuous function of depth in a beam of high‐energy helium ions from the Berkeley 184‐inch synchrocyclotron. Cells were exposed while attached to plastic coverslips in holders that spaced them 0.25 cm apart along the beam path. In some samples oxygen was removed from the medium by metabolic depletion by freshly‐irradiated cells. The original beam energy (910 MeV) was degraded by absorbers so that the residual range was 10 cm; a reciprocating ridge filter then spread the Bragg peak out to a width of 5.5 cm. Cell survival decreased as a function of depth, and the RBE of this beam at maximum depth (highest LET) was 1.4. At this point the OER was 2.2 ± 0.2, compared to 3.0 ± 0.3 at the point where the minimum‐LET beam entered the sample. At the minimum depth to which the Bragg peak was spread, the RBE was 1.1, and the OER was 2.3 ± 0.3. Beyond the stopping point of the beam there was no cell death detectable within the sensitivity of the experiments; for example, surviving fraction was 0.99 ± 0.05 at a point 0.5 cm beyond where the dose was 765 rads.